物种数量（丰富度）下降有害于生态系统，而保护工作则基本上以保护或恢复特定稀有物种为重点。然而，物种相对风度（均匀度）之间更大的差别也可能对生态有害，而这种状况只能通过同时改变很多物种的密度来逆转。
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对以传统方式管理的有机土豆地所做的一项新的调查表明，物种均匀度在有机管理方式下更大。在一项田间试验中，研究人员对这些层次的均匀度进行复制，其结果表明，有机地里所发现的天敌的均匀度可以促进害虫控制和增加作物生物质。在有机作物中，很多有益物种（吃害虫的物种）同样普遍，对土豆来说这样会导致害虫更少、植株更大。(生物谷Bioon.net)
生物谷推荐原文出处：
Nature doi:10.1038/nature09183
Organic agriculture promotes evenness and natural pest control
David W. Crowder,Tobin D. Northfield,Michael R. Strand& William E. Snyder
Human activity can degrade ecosystem function by reducing species number (richness)1, 2, 3, 4 and by skewing the relative abundance of species (evenness)5, 6, 7. Conservation efforts often focus on restoring or maintaining species number8, 9, reflecting the well-known impacts of richness on many ecological processes1, 2, 3, 4. In contrast, the ecological effects of disrupted evenness have received far less attention7, and developing strategies for restoring evenness remains a conceptual challenge7. In farmlands, agricultural pest-management practices often lead to altered food web structure and communities dominated by a few common species, which together contribute to pest outbreaks6, 7, 10, 11. Here we show that organic farming methods mitigate this ecological damage by promoting evenness among natural enemies. In field enclosures, very even communities of predator and pathogen biological control agents, typical of organic farms, exerted the strongest pest control and yielded the largest plants. In contrast, pest densities were high and plant biomass was low when enemy evenness was disrupted, as is typical under conventional management. Our results were independent of the numerically dominant predator or pathogen species, and so resulted from evenness itself. Moreover, evenness effects among natural enemy groups were independent and complementary. Our results strengthen the argument that rejuvenation of ecosystem function requires restoration of species evenness, rather than just richness. Organic farming potentially offers a means of returning functional evenness to ecosystems.
